Aspects of the invention can relate to certain molecules which are susceptible to decomposition by UV light particularly those having a hydrophobic and/or lipophobic structural component. Such molecules may be used to form a monomolecular film which can be photo-patterned when image-wise exposed to low energy UV irradiation. Further, the invention relates a method of forming a film pattern using a technique of discarding tiny droplets such as an ink-jet method, particularly a method of forming a film pattern which is capable of changing solid-state property of the solid-phase surface, or a method of forming a film pattern having reactivity.
Related art methods for forming patterned films on substrate, such as semiconductor substrates can include methods based upon dissolving a photosensitive polymer material in a solvent and then forming a film of this material by spin coating on a semiconductor substrate. The resulting film is then irradiated with ultraviolet rays (UV) through a patterned mask resulting in the formation of a negative or a positive pattern in the photosensitive polymer film. However, the technique of spin coating is inefficient insofar as up to 99% by weight of the polymer material is discarded during the coating step.
As an improvement of such processes, it has been proposed to form photopatternable films of monomolecular thickness which can be imaged by exposure to UV irradiation. These films are called Self-Assembled Monolayers (SAMs). Examples of such methods are disclosed in Micropatterning of organosilane self-assembled monolayers using vacuum ultraviolet light at 172 nm: resolution evaluation by Kelvin-probe force microscopy by H. Sugimura et al., pages 169-170 in Surface Coating Technology (2003) and Scanning probe nanolithography by H. Sugimura page 1182 of Vol. 70, in OYO BUTURI (Applied physics in Japan). Methods using SAMs reduce wastage of the photopatternable material compared to processes which make use of spin coating. This is because only a very small amount of photosensitive material is needed, i.e., the amount needed to form a monomolecular film of the material.
However, the previously proposed photopatternable SAMs have the disadvantage that they have needed to be exposed to high energy UV irradiation for a long period of time in order to be satisfactorily imaged. This means that they have relatively poor processing efficiency. It is desirable therefore to provide an improved material for forming a SAM which can be photo-patterned by exposure to low energy UV irradiation, that is by exposure to UV light having a relatively long wavelength, for a short period of time.
Separately from the above, Dunkin et al, disclose in J. Chem. Soc. Perkin Trans. 2, (2001), page 1414 page 1414 in J. Chem. Soc., Perkin Trans.2, (2001) that an o-nitrobenzyl ester derivative absorbs UV radiation at approximately 254 nm. This absorption induces photoisomerization and photodecomposition reactions.
This is illustrated in the following reaction scheme:

The first reaction in the above scheme is the intramolecular enolization reaction of an o-nitrobenzyl ester derivative. This enolization reaction in turn induces intramolecular cyclization. An ester group present at the benzyl group then dissociates thereby forming a compound having an aldehyde and a nitroso group as a decomposition product. When a carbamic ester linkage is formed at the benzyl group, an amine compound and carbon dioxide are also formed as the other decomposition products.
The present inventors had the idea that derivatives of this type including a photodegradable structural component could be incorporated into a SAM useful for photo-patterning which could be formed on a variety of different substrate types. They further had the idea that such a SAM could be arranged to express two different surface properties of on the one hand hydrophobicity and/or lipophobicity and on the other hand hydrophilicity by means of careful molecular design such that when the molecule is subjected to UV irradiation, the hydrophobic and/or lipophobic structural component is cleaved away liberating a hydrophilic substituent.
In recent years, a technology is required in which DNA, a biological molecule such as antibody and compounds having reactivity with them are fixed onto a solid-phase surface with high dense and high accurate pattern so as to develop a biosensor detecting a specific biological molecule from a test sample and lab-on-chip technology implementing micro-sized biochemical experiments on a glass chip.
As a method of fixing DNA onto a substrate surface with high density, it has been proposed in the pages 5022 to 5026 in Proceedings of the National Academy of Sciences. Vol. 91(1994) by Pease, A. et al. that light is irradiated on a self-assembled monomolecular film having an photo-cleaved protective group with using a photo mask for example forming a pattern of a hydroxyl group, which is specifically reactive, then compounds having four different bases are reacted each other extending one DNA chain.
A method using a photo mask, however, faces difficulty in adjustment of alignment at the time of exposure reaction, resulting in low yield and high manufacturing cost with insufficient detecting sensitivity. On the other hand, as a method of forming tiny film pattern on a surface of solid substrate, a means of ejecting micro droplets such as ink-jet method is used. The device for ejecting micro droplets enables a material included in a droplet to be supplied to a specific position on the substrate by ejecting a droplet with moving a stage on which a solid phase group is installed.
Therefore, in such case when biological molecules or compounds are fixed with giving direct pattern, it is efficient that pre-processes such as forming a region being reactive with these biological molecules or compounds and controlling a solid-state property such as wettabililty, are implemented to a surface of a substrate. According to such processes, preferably trapping a material to be fixed in a targeted region and preventing it from being attached to other region can be possible.